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Myopalladin, a novel 145-kilodalton sarcomeric protein with multiple roles in Z-disc and I-band protein assemblies.

Bang ML, Mudry RE, McElhinny AS, Trombitás K, Geach AJ, Yamasaki R, Sorimachi H, Granzier H, Gregorio CC, Labeit S - J. Cell Biol. (2001)

Bottom Line: Both sites are highly homologous with those found in palladin, a protein described recently required for actin cytoskeletal assembly (Parast, M.M., and C.A.Overexpression of myopalladin's NH(2)-terminal CARP-binding region in live cardiac myocytes resulted in severe disruption of all sarcomeric components studied, suggesting that the myopalladin-CARP complex in the central I-band may have an important regulatory role in maintaining sarcomeric integrity.Our data also suggest that myopalladin may link regulatory mechanisms involved in Z-line structure (via alpha-actinin and nebulin/nebulette) to those involved in muscle gene expression (via CARP).

View Article: PubMed Central - PubMed

Affiliation: European Molecular Biology Laboratory, Heidelberg 69117, Germany.

ABSTRACT
We describe here a novel sarcomeric 145-kD protein, myopalladin, which tethers together the COOH-terminal Src homology 3 domains of nebulin and nebulette with the EF hand motifs of alpha-actinin in vertebrate Z-lines. Myopalladin's nebulin/nebulette and alpha-actinin-binding sites are contained in two distinct regions within its COOH-terminal 90-kD domain. Both sites are highly homologous with those found in palladin, a protein described recently required for actin cytoskeletal assembly (Parast, M.M., and C.A. Otey. 2000. J. Cell Biol. 150:643-656). This suggests that palladin and myopalladin may have conserved roles in stress fiber and Z-line assembly. The NH(2)-terminal region of myopalladin specifically binds to the cardiac ankyrin repeat protein (CARP), a nuclear protein involved in control of muscle gene expression. Immunofluorescence and immunoelectron microscopy studies revealed that myopalladin also colocalized with CARP in the central I-band of striated muscle sarcomeres. Overexpression of myopalladin's NH(2)-terminal CARP-binding region in live cardiac myocytes resulted in severe disruption of all sarcomeric components studied, suggesting that the myopalladin-CARP complex in the central I-band may have an important regulatory role in maintaining sarcomeric integrity. Our data also suggest that myopalladin may link regulatory mechanisms involved in Z-line structure (via alpha-actinin and nebulin/nebulette) to those involved in muscle gene expression (via CARP).

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Myopalladin is a novel 145-kD protein with homology to palladin. (A) Comparison of the domain architecture of myopalladin and the recently described palladin protein (Parast and Otey 2000). The Ig-I repeats are shown in gray, the unique sequences are shown in white, and the proline-rich PPP motif regions are shown in black. The bars above the myopalladin and below the palladin schematics indicate the recombinant fragments of the proteins that were used as antigens to generate specific antibodies (see Fig. 7 for the characterization of the antibodies). (B) Dot plot matrix sequence comparison of myopalladin and palladin. The regions of myopalladin and palladin that bind to the nebulin SH3 domain and to α-actinin are the most conserved regions between the two proteins. (C) Peptide sequence alignment of myopalladin's five Ig-I domains and comparison with Ig-I domains from myotilin (EMBL/GenBank/DDBJ accession number AF144477), titin N2B (accession number X90568), and palladin (accession number AB023209). All sequences are from humans. Identical residues are indicated by asterisks. (D) Phylogenetic tree based on the comparison of myopalladin's Ig-I repeats and the most related Ig-I repeats from myotilin, titin, and palladin.
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Figure 2: Myopalladin is a novel 145-kD protein with homology to palladin. (A) Comparison of the domain architecture of myopalladin and the recently described palladin protein (Parast and Otey 2000). The Ig-I repeats are shown in gray, the unique sequences are shown in white, and the proline-rich PPP motif regions are shown in black. The bars above the myopalladin and below the palladin schematics indicate the recombinant fragments of the proteins that were used as antigens to generate specific antibodies (see Fig. 7 for the characterization of the antibodies). (B) Dot plot matrix sequence comparison of myopalladin and palladin. The regions of myopalladin and palladin that bind to the nebulin SH3 domain and to α-actinin are the most conserved regions between the two proteins. (C) Peptide sequence alignment of myopalladin's five Ig-I domains and comparison with Ig-I domains from myotilin (EMBL/GenBank/DDBJ accession number AF144477), titin N2B (accession number X90568), and palladin (accession number AB023209). All sequences are from humans. Identical residues are indicated by asterisks. (D) Phylogenetic tree based on the comparison of myopalladin's Ig-I repeats and the most related Ig-I repeats from myotilin, titin, and palladin.

Mentions: Analysis of the primary structure of myopalladin revealed the presence of five Ig domains from the Ig-I subset (Harpaz and Chothia 1994; designated I–V in Fig. 2 A) in its 1,320-residue sequence. Six interdomain insertions (designated IS1–IS6) separate the five Ig repeats. To search for proteins homologous to myopalladin, a BLAST search was performed with its 145-kD peptide sequence (BLAST2 from the National Center for Biotechnology Information server). From known proteins, Ig repeats from palladin (human: EMBL/GenBank/DDBJ under accession number AB023209; mouse: Parast and Otey 2000) (68% identity), the Z-disc protein myotilin (Salmikangas et al. 1999) (50% identity), and titin's central I-band N2B region (48% identity) were most related to myopalladin (Fig. 2 C). The two NH2-terminal Ig domains in myopalladin are most homologous to Ig domains from the N2B region of titin in the I-band region. Myopalladin's three COOH-terminal Ig domains are most related to palladin's Ig domains, whereas the two most COOH-terminal Ig domains also share high homology to myotilin's Ig domains (Fig. 2 D).


Myopalladin, a novel 145-kilodalton sarcomeric protein with multiple roles in Z-disc and I-band protein assemblies.

Bang ML, Mudry RE, McElhinny AS, Trombitás K, Geach AJ, Yamasaki R, Sorimachi H, Granzier H, Gregorio CC, Labeit S - J. Cell Biol. (2001)

Myopalladin is a novel 145-kD protein with homology to palladin. (A) Comparison of the domain architecture of myopalladin and the recently described palladin protein (Parast and Otey 2000). The Ig-I repeats are shown in gray, the unique sequences are shown in white, and the proline-rich PPP motif regions are shown in black. The bars above the myopalladin and below the palladin schematics indicate the recombinant fragments of the proteins that were used as antigens to generate specific antibodies (see Fig. 7 for the characterization of the antibodies). (B) Dot plot matrix sequence comparison of myopalladin and palladin. The regions of myopalladin and palladin that bind to the nebulin SH3 domain and to α-actinin are the most conserved regions between the two proteins. (C) Peptide sequence alignment of myopalladin's five Ig-I domains and comparison with Ig-I domains from myotilin (EMBL/GenBank/DDBJ accession number AF144477), titin N2B (accession number X90568), and palladin (accession number AB023209). All sequences are from humans. Identical residues are indicated by asterisks. (D) Phylogenetic tree based on the comparison of myopalladin's Ig-I repeats and the most related Ig-I repeats from myotilin, titin, and palladin.
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Related In: Results  -  Collection

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Figure 2: Myopalladin is a novel 145-kD protein with homology to palladin. (A) Comparison of the domain architecture of myopalladin and the recently described palladin protein (Parast and Otey 2000). The Ig-I repeats are shown in gray, the unique sequences are shown in white, and the proline-rich PPP motif regions are shown in black. The bars above the myopalladin and below the palladin schematics indicate the recombinant fragments of the proteins that were used as antigens to generate specific antibodies (see Fig. 7 for the characterization of the antibodies). (B) Dot plot matrix sequence comparison of myopalladin and palladin. The regions of myopalladin and palladin that bind to the nebulin SH3 domain and to α-actinin are the most conserved regions between the two proteins. (C) Peptide sequence alignment of myopalladin's five Ig-I domains and comparison with Ig-I domains from myotilin (EMBL/GenBank/DDBJ accession number AF144477), titin N2B (accession number X90568), and palladin (accession number AB023209). All sequences are from humans. Identical residues are indicated by asterisks. (D) Phylogenetic tree based on the comparison of myopalladin's Ig-I repeats and the most related Ig-I repeats from myotilin, titin, and palladin.
Mentions: Analysis of the primary structure of myopalladin revealed the presence of five Ig domains from the Ig-I subset (Harpaz and Chothia 1994; designated I–V in Fig. 2 A) in its 1,320-residue sequence. Six interdomain insertions (designated IS1–IS6) separate the five Ig repeats. To search for proteins homologous to myopalladin, a BLAST search was performed with its 145-kD peptide sequence (BLAST2 from the National Center for Biotechnology Information server). From known proteins, Ig repeats from palladin (human: EMBL/GenBank/DDBJ under accession number AB023209; mouse: Parast and Otey 2000) (68% identity), the Z-disc protein myotilin (Salmikangas et al. 1999) (50% identity), and titin's central I-band N2B region (48% identity) were most related to myopalladin (Fig. 2 C). The two NH2-terminal Ig domains in myopalladin are most homologous to Ig domains from the N2B region of titin in the I-band region. Myopalladin's three COOH-terminal Ig domains are most related to palladin's Ig domains, whereas the two most COOH-terminal Ig domains also share high homology to myotilin's Ig domains (Fig. 2 D).

Bottom Line: Both sites are highly homologous with those found in palladin, a protein described recently required for actin cytoskeletal assembly (Parast, M.M., and C.A.Overexpression of myopalladin's NH(2)-terminal CARP-binding region in live cardiac myocytes resulted in severe disruption of all sarcomeric components studied, suggesting that the myopalladin-CARP complex in the central I-band may have an important regulatory role in maintaining sarcomeric integrity.Our data also suggest that myopalladin may link regulatory mechanisms involved in Z-line structure (via alpha-actinin and nebulin/nebulette) to those involved in muscle gene expression (via CARP).

View Article: PubMed Central - PubMed

Affiliation: European Molecular Biology Laboratory, Heidelberg 69117, Germany.

ABSTRACT
We describe here a novel sarcomeric 145-kD protein, myopalladin, which tethers together the COOH-terminal Src homology 3 domains of nebulin and nebulette with the EF hand motifs of alpha-actinin in vertebrate Z-lines. Myopalladin's nebulin/nebulette and alpha-actinin-binding sites are contained in two distinct regions within its COOH-terminal 90-kD domain. Both sites are highly homologous with those found in palladin, a protein described recently required for actin cytoskeletal assembly (Parast, M.M., and C.A. Otey. 2000. J. Cell Biol. 150:643-656). This suggests that palladin and myopalladin may have conserved roles in stress fiber and Z-line assembly. The NH(2)-terminal region of myopalladin specifically binds to the cardiac ankyrin repeat protein (CARP), a nuclear protein involved in control of muscle gene expression. Immunofluorescence and immunoelectron microscopy studies revealed that myopalladin also colocalized with CARP in the central I-band of striated muscle sarcomeres. Overexpression of myopalladin's NH(2)-terminal CARP-binding region in live cardiac myocytes resulted in severe disruption of all sarcomeric components studied, suggesting that the myopalladin-CARP complex in the central I-band may have an important regulatory role in maintaining sarcomeric integrity. Our data also suggest that myopalladin may link regulatory mechanisms involved in Z-line structure (via alpha-actinin and nebulin/nebulette) to those involved in muscle gene expression (via CARP).

Show MeSH